Apparatus for lowering and raising a shipping cask for spent nuclear fuel into a storage pool

ABSTRACT

Apparatus and method for lowering and raising a shipping cask into a storage pool for receiving spent nuclear fuel assemblies is described. The apparatus comprises a secondary support system installed in the pool for vertical movement of the cask in the pool. The secondary support system is capable of fully supporting the cask in case of failure of the usual overhead hoist system. A feature provides for lowering and raising of the cask in at least two steps, enabling addition of an extension piece to the overhead crane hook after the cask has been at least partly immersed to avoid immersion of the crane hook, sheaves and cable into the storage pool. Still another feature is provision of a substantially water-tight removable shroud for the cask preventing direct contact of the cask exterior with the storage pool fluid to avoid contamination thereof.

United States Patent [191 Jones 1 APPARATUS FOR LOWERING AND RAISING ASHIPPING CASK FOR SPENT NUCLEAR FUEL INTO A STORAGE POOL [75] Inventor:

[73] Assignee:

Cecil R. Jones, Hamden, Conn.

Related US. Application Data [63] Continuation-impart of Ser. No.124,228, March 15,

1971, abandoned.

[52] US. Cl. 214/16 B, 187/68 [51] Int. Cl B65g l/04, G2lc 19/32 [58]Field of Search..... 214/16 B, 17 R, 17 B, 17 C,

[56] References Cited UNITED STATES PATENTS 750,597 1/1904 Carnes 187/683,533,911 10/1970 Fortescue et a1. 176/30 [4 June 25, 1974 PrimaryExaminer-Robert G. Sheridan 1 5 7] ABSTRACT Apparatus and method forlowering and raising a shipping cask into a storage pool for receivingspent nuclear fuel assemblies is described. The apparatus comprises asecondary support system installed in the pool for vertical movement ofthe cask in the pool. The secondary support system is capable of fullysupporting the cask in case of failure of the usual overhead hoistsystem. A feature provides for lowering and raising of the cask in atleast two steps, enabling addition of an extension piece to the overheadcrane hook after the cask has been at least partly immersed to avoidimmersion of the crane hook, sheaves and cable into the storage pool.Still another feature is provision of a substantially water-tightremovable shroud for the cask preventing direct contact of the caskexterior with the storage pool fluid to avoid contamination thereof.

12 Claims, 11 Drawing Figures PATENIEDJUN25I974 v 3.819.066

sum 2 or 5 I --Z8a l I 2e 28 INVENTOR CECIL R. JONES BY k M'LI/WATTORNEY PIIIIEIIIIIIIIM 3.819.066 A sum 3 or 5 I I I II|I III HOIST IIIII U IZO oz- PRESSURE Fig.7 88 TIE? I I I? I I I I I I I I I I I I I II I I 183 I as i I I I2I I I I 1 ENT CEC R. J ES ATTORNEY PATENIEDJUN 255174 SHEET 0F 5 INVIIUOR. CECIL R. JONES ATTORNEY PATENTED June 5 1924sum 5 or 5 INVENTOR. CECIL R. JONES ATTORNEY:

APPARATUS FOR LOWERING AND RAISING A SHIPPING CASK FOR SPENT NUCLEARFUEL INTO A STORAGE FL This invention relates to apparatus and a methodfor lowering and raising a shipping cask for spent nuclear fuel into andfrom fuel storage pool. This application is a continuation-in-part of myprior application, Ser. No. 124,228 filed Mar. 15, 1971 now abandoned.

BACKGROUND OF THE INVENTION Spent nuclear fuel assemblies after removalfrom power-generating nuclear reactors are stored in a fuel storage poolusually located adjacent the reactor well. Disposal of such fuelinvolves its placement in a shipping cask, followed by shipment of thecask to a fuel reprocessing plant. Such casks are usually made of lead,and have a sufficient length to accommodate the conventional fuelassemblies. A typical cask having an inside diameter of about 3 to feet,an outside diameter of about 5 to 8 feet, and a length of about to 17feet, would weigh from about 70 to 120 tons. To maintain a protectedenvironment, the cask is lowered into the fuel storage pool, the spentfuel assemblies placed into the cask and the cask closed, all whileunder water, and then the loaded cask removed from the pool,decontaminated, and made ready for shipping. To prevent exposure of thespent fuel rods which are still radioactive, generally the pool has adepth more than the combined length of the cask and the fuel assemblies,for example forty feet in depth. Lowering and raising of the cask isaccomplished by the. usual overhead crane and attached hoists.

The above procedure involves a number of serious problems. Firstly,there is no double load path for the cask during its lowering andraising into and from the pool. Should the hoist cables fail, thefalling cask could have catastrophic effects, such as for examplecracking of the pool floor causing draining of the shielding pool waterand exposure of the radioactive fuel assemblies stored therein.Secondly, the pool water is often contaminated due among other things toleaking fuel rods in the spent fuel assemblies. This contaminates thecask surface, requiring its decontamination after removal from the pool.Thirdly, most existing power stations do not have sufficient headroom inthe reactor building to accommodate a hoist capable of handling a solidextension piece of some twenty feet in length attached to the crane hookin addition to the fifteen or so feet of height of the cask. What thismeans is that the hook, sheaves and cables of the hoist attached to thecask necessarily become immersed in the pool, causing theircontamination. Decontamination of such equipment, especially cables, isextremely burdensome.

The main objects of the present invention are apparatus and methods forhandling a shipping cask to be loaded with spent fuel assemblies in astorage pool providing one or more of the following:

1. continuous double load path for cask support providing protectionagainst accidental failure or operator mishandling of the primarysupport overhead hoist system;

2. avoidance of immersion of the overhead crane hook, sheaves and cablesinto the storage pool fluid; and

. 3. avoidance of direct contact between the cask exterior and thestorage pool fluid.

SUMMARY OF THE INVENTION These and other objects of the invention aswill appear hereinafter are achieved by installing in the stor age poola secondary cask support system for lowering and raising of the shippingcask and capable of fully supporting the cask at all times in case offailure of the primary overhead hoist. A further feature of theinvention is the provision of at least one intermediate stop arrangementin the pool cask support system enabling the cask to be lowered andraised in two or more steps whereby an extension piece can be added tothe overhead crane hook after the cask has been partially lowered intothe pool to avoid immersion of the crane hook, sheaves and cables intothe storage pool fluid. Still another feature of the invention is acable-less secondary cask support system affording reduced maintenance.A further feature is a secondary cask support employing hydrauliccylinders wherein the direct cask support is secured to and movable withthe cylinders rather than to the pistons. A further feature of thelatter construction is a hydraulic cylinder construction whose lengthneed be no greater than substantially onehalf the pool depth. Still afurther feature of the invention is the provision of a substantiallywater tight removable shroud surrounding the cask to prevent directcontact between the pool fluid and the cask outer surface to avoidcontamination thereof.

Other features and advantages of the invention will I become apparentfrom the following detailed descriptionof several embodiments thereoftaken in conjunction with the accompanying drawings wherein:

DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic front elevationview of a first embodiment of the apparatus of the present invention forlowering a spent nuclear fuel shipping cask into a storage pool.

FIG. 2 is a plan view of the apparatus shown in FIG. I.

FIG. 3 is a side elevation view of the apparatus shown in FIGS. 1 and 2.

FIG. 4 is an enlarged, fragmentary elevation view taken along line 44 ofFIG. 1.

FIG. Sis an enlarged, fragmentary elevation view taken along line 55 ofFIG. 3.

FIG. 6 is an enlarged sectional view taken along line 66 of FIG. I toillustrate the counterbalancer and velocity limiter employed in theapparatus shown in FIG. 1.

FIG. 7 is a diagrammatic front elevation view of a second embodiment ofthe present invention.

FIG. 8 is a perspective view of the upper part of the apparatus shown inFIG. 7.

FIG. 9 is a fragmentary view of part of the platform and cylindersupport of the apparatus of FIG. 7.

FIG. 10 is a partial front elevation view of the apparatus of FIG. 7with the platfonn at mid position.

FIG. 11 is front partially sectional, partially elevation view of theshroud surrounded cask.

DESCRIPTION OF CABLE EMBODIMENT Illustrated in FIGS. 1-3 is one form ofan apparatus 10 of the present invention for lowering a spent nuclearfuel shipping cask 15 into a conventional fuel storage pool P containingrelatively pure water W. Conventionally, an irradiated fuel shippingcask is of lead depleted uranium or other high density shieldingmaterial. It is also well-known that water W in the fuel storage pool Palso serves as a radioactive shielding material for spent nuclear fuelstored in the pool, and may also be included for shielding purposes inthe shipping cask 15.

The apparatus comprises four upright, tubular water-tight posts -23 ofsuitable corrosion-resistant material, such as stainless steel, whichserve as cylinders of a hydraulic system. The feet of the posts 20-23are fixedly secured by suitable means to the walls surrounding'the poolP and to the floor of the fuel storage pool P. Suitable braces 24 areemployed to reduce flexure of the posts 20-23. Disposed within the posts20-22, respectively, in water tight engagement therewith, arecounterbalancers and velocity limiters 25-27 which constitute the pistonpart of the hydraulic system. The counterbalancer and velocity limiterfor the post 23 is not shown, but it is similar to the counterbalancerand velocity limiter 26 shown in FIG. 6 for the post 21.

Mounted on the upper ends of the posts 20-23, respectively, for freerotation are pulleys 30-33 by means of brackets -38. Trained around thepulleys 30-33 'are suitable stainless steel cables 40-43 respectively,with plastic covers. Suitable retainers 34 (FIGS. 4 and 5) on thebrackets 35-38 hold the cables 40-43 onto the associated pulleys 30-33.One of the runs of the cables 40-43 are disposed within the posts 20-23and are attached to the piston counterbalancers and velocity limiters25-28, respectively. The counterbalancers and velocity limiters 25-28are movable in the vertical direction within the posts 20-23. As shownin FIG. 6, seals and guides, such as seals 28a on the .counterbalancerand velocity limiter 26 provide sealing engagement with the inner wallof the associated post. On top of the posts 20-23, respectively, andsurrounding the cables 40-43, respectively, are suitable seals (FIG. 5)for maintaining the upper ends of the posts 20-23 relatively watertight. Water or a suitable fluid F (FIG. 5) is disposed in the posts20-23 below the seals 4548 and above the counterbalancersv and velocitylimiters 25-28.

The other runs of the cables 40-43 extend out of the posts 20-23 and areattached to a shipping cask platform support for supporting the same.The fuel pool cask support 50 is made of suitable material, such asstainless steel. As shown in FIG. 2, the shipping cask support 50 islocated between the posts 20-23. Seated on the shipping cask support 50is the cylindrical fuel shipping cask 15.

Under no load condition, the shipping cask support 50 is in the elevatedposition (FIGS. 1 and 2) and the counterbalancers and velocity limiters25-28 are at the base of the associated posts 20-23. Formed on.the upperportion of theshipping cask 15 are suitable trunnions 56 and 57. Aconventional overhead crane, not shown, with a cable, sheave and grappleor hook engages the trunnions 56 and 57 to support, to lower and toraise, and to transport the fuel shipping cask 15. Initially, theshipping cask platform 50 is in the no load position and the crane withthe cable and hook lowers the shipping cask 15 to seat upon the shippingcask support 50. Prior to or at this time, a conventional lid or coveris removed from the shipping cask 15. Then suitable stops (not shown)are removed from under the support 50. As the overhead crane releasesthe cask load, it slowly sinks on the platform into the water pool underits own weight until the platform 50 engages interrnediate plunger seatsor stops 60-63 and comes to a dead stop. The system is designed so thata suitable fraction, for example, approximately -80 percent of the caskload, is taken up by the secondary support system leaving the remainingof 20-30 percent of the load to be carried by the overhead crane andhoist. This is readily controlled by adjustment of the velocitylimiters. With the cask partly immersed but stopped before the trunnions56 and 57 have entered the water, as shown in phantom in FIG. 1, anoperator then removes the crane cable and hooks from the trunnions 56and 57 of the fuel shipping cask 15 and attaches one end of aconventional extension piece or sling, not shown, to the free end of thecrane cable and hook. The other end of the extension piece with a hookthereon is attached to the trunnions of the fuel shipping cask 15 toonce again support the same from the crane, not shown. If desired, ashort extension piece can be attached to the cask trunnions. This allowsthe cask to be lowered to a deeper level before stopping and adding thelong extension piece. Now, the shipping cask 15 is first raised slightlyby the overhead hoist to permit removal of the plunger seats 60-63 fromunder the platform, and then lowering of the cask is continued until itsbase rests on the floor of the fuel pool P via the shipping cask support50. Spent nuclear fuel is loaded into the shipping cask 15 while theshipping cask 15 rests on the floor of the pool P. After fully loadingthe shipping cask 15 with spent nuclear fuel, the lid or cover is againfitted on the top of the shipping cask 15.

Mounted on the posts 20-23 a predetermined distance from the respectivetops thereof are the remotely activated platform seats, only seats 60and 61 are shown (FIGS. 4 and 5), respectively, which are operatedthrough air under pressure in a suitable air cylinder, such as aircylinders 62-64. The plunger type seats 60-61 are extended into thedownward path of travel of the crane support 50 to support same when anoperator remotely activates the associated air cylinders 62-64 to extendthe seats 60-61. When an operator remotely removes the air underpressure in the air cylinders, a spring retracts the plunger type seatto remove the same from the path of travel of the downward movement ofthe crank support 50.

A valve 70 and suitable conduits 71-73 are mounted on the posts 20-23 tocontrol the rate of flow of water trapped in the posts 20-23 between theseals 45 and the counterbalancer and limiters 25-28 from escaping fromthe posts 20-23 into a suitablefilter, not shown. The valve 70 and theconduits 71-73 are arranged to maintain the same water pressure head ineach post 20-23. More specifically, should the fuel shipping cask 15drop accidentally, because the crane cable breaks, or the hook isinadvertently removed from the trunnions 56 and 57 of the shipping cask15, or should the crane lower the shipping cask 15 at too fast avelocity, the water in the posts 20-23 between the seals 45 and thecounterbalancers and velocity limiters 25-28, respectively, is trappedto produce a braking action to the dropping or lowering of the casksupport 50. The rate at which the trapped water flows through theconduits 71-73 and valve 70 into the filter, not shown, controls themaximum velocity at which the shipping cask and its cask support 50 maybe dropped or lowered. Thus, the rate at which the laden shipping caskis dropped or lowered is decelerated by the water trapped in the posts20-23. The maximum velocity of the dropping or lowering of the ladenshipping cask is regulated by adjusting the deceleration control valve70 to control the rate of flow of trapped water therethrough.

While this embodiment shows a braking action through trapped water, itis apparent that gas, air, or other fluids under pressure may beemployed equally as well. For example, a cylinder of gas under pressurecan communicate with the posts 23 to supply gas under pressure theretoand a return path to the cylinder of gas of the gas escaping from theposts under a rate controlled by suitable and well-known valves. A pumpmay be connected to the cylinder of gas for maintaining suitablepressure therein. A pump, not shown, may also be connected to theconduit exiting from the valve 70. During raising of the cask 15 by theoverhead hoist, water can be pumped under pressure into the postsdriving the pistons 25-28 downward and lifting the platform 50 under theascending cask to provide additional support therefor and continue thesecondary support for the cask while it is being lifted out of the pool.The hydraulic system can be completely closed with its own water supply,or connected to the pool supply to draw water downstream of the poolwater supply filter.

DESCRIPTION OF CABLELESS EMBODIMENT The first embodiment above describedemploys cables which come in contact with the pool water, and which areconnected to pistons moving in elongated fixed cylinders anchored to thestorage pool. Cables involve certain maintenance problems whoseelimination may be preferable at existing reactor facilities. Inaddition, the construction of water-tight cylinders having the full pooldepth may not be feasible in those facilities lacking adequate space forinstallation of such long cylinders. This second embodiment to be nowdescribed and which is my preferred embodiment avoids the use of cablesand requires cylinder lengths substantially no more than one-half thepool depth.

Referring now to FIGS. 7-10, the cask secondary support system comprisestwo generally H-shaped main supports 80 which extend the full depth ofthe pool and are anchored and fixed therein. The top support for theH-shaped members 80 comprises elements 81, 82 anchored to the refuelingfloor 79 and which secure the members 80 in a corner of the pool.Reinforcement at the bottom is provided by struts 83. As is normal, thevarious parts of this structure that are immersed in the pool areconstituted of suitable corrosion-resistant materials, such asstainless-steel. Four hydraulic cylinders 85 are provided. Each cylinder85 contains a suitable piston 86 and fittings 87, only one of which areshown, at opposite ends of the cylinder for introducing and withdrawingfluid within each cylinder above and below the piston. Pipes 88connected to the fittings 87 ultimately are connected to suitablevalves, pumps, sumps, controls, etc., all well known in the art andtherefore not illustrated herein, for the purpose of controlling thefluid pressure above and below the pistons. Each piston 86 is connectedto a solid connecting rod 90 which passes through a hole in the uppersupport elements 81, 82 and forms an enlarged member terminating in aneye bolt 89. The cylinders are supported by and are suspended from theupper support elements 81, 82 via the piston connecting rod 90.

A cask platform 91 is supported on the cylinders 85. The cask platformcomprises a floor 92, side walls 93, and a rear wall 94 dimensioned toaccommodate the cask bottom. The platform corners are each provided withprojections 95 which enbrace 97, the adjacent support 80 and eachcontaining a rectangular opening 1 96. All the rectangular openings areoriented in the same direction. Each of the cylinders contain at theirtop end two oppositely disposed lugs 100. The dimension across the topof the lugs 100 is longer than the short side of the rectangular opening96 but shorter than the long side of the rectangular opening. Thus inthe position illustrated in FIGS. 7-9, the projections abut the lugs 100and the platform 91 is thus supported by the four cylinders 85. At thebottom of the cylinders 85 are provided two similarly dimensioned lowerlugs 101 but oriented at right angles to the upper lugs 100. With theplatform load lifted off the cylinders 85, each of the connecting rods90 can be lifted via their eye bolts 89, rotated 90 until the upper lugs100 are oriented in the long dimension of the opening 96, and then thecylinder pulled through the opening or the platform lowered until thelower cylinder lugs 101 are contacted, which will now, due to their 90rotation, be oriented to contact the projection 95. This allows theplatform to be supported alternatively by the lower cylin- I der lugs101 or by the upper cylinder lugs 100. It is also possible to provideprojection openings that are square rather than rectangle. In this case,the dimension across the top of the lugs must be larger than the squareside but smaller than a diagonal of the square opening. Passage of thelugs through the opening is then obtained by a 45 rotation, andreengagement by the bottom lugs obtained with a second 45 rotation.

Two stop systems for the platform 91 are provided. The first, similar tothat of the first embodiment, comprises electrically activated solenoids103 mounted at the top of the side supports 80 just under the platform91 in its upper rest position. Until these are activated, the platform91 cannot descend. Suitable sensors can be located in the platform floorfor activating an interlock system (not shown) which prevents removal ofthe upper stops unless the cask is properly positioned on the platform..The second stop system 104 is located approximately at the center ofthe side supports 80, and they may in this case comprise oppositeshelves which can be manually activated into or out of the downward pathof travel of the platform 91. If desired, an electrically orpneumatically activated stop system can be substituted for the manualsystem illustrated.

Before the cask 15 is loaded onto the platform 91, it is firstpreferably seated in a flanged base member 105 (see FIG. 11) whoseflange 106 is secured as by a tightening strap 107 to the cask bottom.Secured to the flange 106 is a flexible substantially water-tight shroud108, for example of plastic reinforced by light metal rings encased inthe plastic to provide horizontal support, which can be manually liftedup to cover the whole length of the cask 15 and there secured inposition as by straps 109 or the like. Suitable openings may be providedin the sides of the shroud 108 for passage of the cask trunnions 56, 57.This is readily provided by soft flexible loops 116 as of stretchablematerial attached to the plastic and stretched over the trunnions tosecure the shroud 108 around and seal to the trunnions. Nipples 113 areprovided at top and bottom of the shroud 108, which can be connected tohoses and a suitable pumping system, not shown, in order to continuouslyflush clean water between the cask exterior and the shroud at aslightly'higher pressure than the pool water to prevent the latter fromentering any small openings in the shroud and thus contact and possiblycontaminate the cask outer surfaces.

Mounted on the refueling floor 79 are two opposed cask guides 115 in theform of channels spaced from each other and above the refueling floor 79a short distance to accommodate the wide bottom of the flanged basemember 105. The cask guide channels 115 extend a short distance in frontof the open side of the platform floor 92, which as will be observedfrom FIG. 7 is located slightly above the plane of the pool curb 116.

In operation, the empty cask is lifted by the overhead hoist, shownschematically at 120 in FIG. 7, and placed into the flanged base member105, the strap 107 tightened, the shroud 108 lifted up to enclose thecask, the loops 1 16 fitted over the trunnions 56, 57, the shroud strap109 tightened, and the nipples 113 secured to its water pumping system,which is activated. Then the cask 15 with attached shroud 108 is liftedand guided into the entrance of the cask guides 115 and then slowlymoved to the right of FIG. 7 until the cask is positioned over thecenter of the platform 91 and then lowered to rest on the platform. Thenthe usual cask cover (not shown) is removed. I

The guides 115 are provided to prevent tilting ofthe cask on amalfunction of the overhead hoist causing the cask to pitch into thestorage pool P. Similarly, the position of the platform floor 91slightly above the pool rim 116 further ensures that the cask will beslightly tilted in a direction away from the pool should the overheadhoist fail. If the cask is properly positioned on the platform, then theupper stops 103 are removed. The platform load is now carried by thefour cylinders 85. By appropriate adjustment of the fluid pressure onopposite sides of the piston.86 to carry approximately 7080 percent ofthe load, as the overhead hoist 120 releases the load, the platform willslowly descend into the pool advancing the cylinders 85 before it whilethe pistons slowly ascend within their respective cylinders, with theoverhead hoist attached.

Before the pistons reach the top of their respective cylinders, theplatform engages the middle stop shelves 104 and comes to a dead stop.The cylinder pressure is now adjusted to cause the cylinders 85 todescend alone to the end of their travel. Next, the connecting rods 90are lifted by their eyebolts 89, rotated 90, and then the cylinder fluidpressure reversed causing the cylinders 85 to be drivenupward, in thisprocess the upper lugs 100 pass through the long side of the rectangularopenings 96 of the platform projections 95. Finally, the lower lugs 101engage the projections 95 and the cylinders 85 stop their upwardmovement. The pistons 86 are now located at the bottom of the cylinders(see FIG. 10.). The connecting rods are lifted a small distance to raisethe platform 91 above the center stops 104, the shelves 104 now movedout of the downward path of travel of the platform, and the cylinderpressure readjusted again to take up 70-80 percent of the cask load.Again, as the overhead hoist releases the load, the platform continuesits descent until it comes to rest on the pool floor 121. As before, thespent fuel elements are loaded into the water filled cask, the coverreplaced, and the procedure reversed to lift the cask and the platformout of the pool. That is to say, adjusting the cylinder pressure drivesthe movable cylinders upward raising the platform with loaded cask tojust above the center stop 104. Then the stop is moved outward and theplatform rested on the center stop. Next the cylinders are drivendownward until the upper lugs 100 pass through the projection openings96, the connecting rods rotated 90, and the upper lugs brought intocontact with the projections 95. Then, the cylinders are againhydraulically driven upward until the platform arrives at its upper restposition shown in FIG. 7, and the upper stops 103 activated to hold theplatform. During substantially this entire lowering and raising process,both the platform and-the overhead hoist, each independently capable oftaking up the full cask load, have been simultaneously supporting thecask providing a continuous double load cask support system. This alsooffers the advantage of limiting the strain on the hoist increasing itslifetime.

As was described in connection with the first embodiment, the descendingempty cask is stopped by the middle stop 104 just before the trunnions56,57 and attached hoist hook, sheaves and cable become immersed in thepool, and at this point an extension sling (not shown) is attached tothe hook to avoid immersion of the latter. The sling, which may besoildand of corrosion-resistant material, and is more easilydecontaminated, becomes the only hoist part immersed in the water. Thuscontamination of the pure water in the pool by a corrosive cable andhook is obviated. Also, the cask shroud 108 has prevented contact of thepool water P with the cask outer surfaces thereby avoiding the necessityfor decontamination thereof.

After the loaded cask has been removed from the platform and exited fromthe pool via the cask guides 115, then the shroud 108 and base 105 maybe removed, and the cask loaded on a suitable carrier for shipment tothe fuel reprocessing plant.

In this second embodiment, no cables are exposed to the contaminatedpool water, and the cylinders need only have a length of about one-halfthe pool depth.

Both embodiments are adapted for installation in presently existing ordesigned reactor facilities to provide protection against malfunction ofthe single overhead hoist system presently used for cask movement.

To avoid the possibility that the cylinder lugs 100, 101 are notproperly seated on the projections 95, the latter can be provided withslots for receiving of the lugs, and sensors, if desired, can be locatedin the slots to prevent movement of the platform if the lugs are notseated in the slots. v

While my invention has been described in connection with specificembodiments thereof, those skilled in the art will recognize thatvarious modifications are possible within the principles enunciatedherein and thus the present invention is not to be limited to thespecific embodiments disclosed.

What is claimed is:

1. Apparatus for supporting a nuclear fuel shipping cask during loweringinto or raising from a storage pool, comprising a mechanical supportingstructure at least partly immersed in and anchored to the pool, a casksupport platform, fluid pressure responsive means supporting saidplatform and mounted on said supporting structure to provide verticalmovement of the platform along a path from an upper position at the pooltop to a lower position at the pool floor, means for controlling thefluid pressure means, mechanical stop means mounted on the supportingstructure intermediate the pool top and floor and selectively movableinto the vertical path of the platform for arresting downward motion ofand supporting the arrested platform, in combination with independenthoist means mounted above the storage pool for engaging and lifting thecask, said mechanical stop being capable of fully supporting the loadedplatform enabling disengagement of the hoist from the cask or of thefluid support for said platform.

2. Apparatus as set forth in claim 1 wherein the fluid pressureresponsive means comprises hydraulic cylinders supporting the platform,said hydraulic cylinders each containing a piston supported by thesupporting structure.

3. Apparatus for supporting a nuclear fuel shipping cask during loweringinto or raising from a storage pool, comprising a supporting structureat least partly immersed in and anchored to the pool, a cask supportplatform, fluid pressure responsive means supporting said platform andmounted on said supporting structure to provide vertical movement of theplatform from an upper position at the pool top to a lower position atthe pool floor, said fluid pressure responsive means comprisinghydraulic cylinders supporting the platform, said hydraulic cylinderseach containing a piston supported by the supporting structure, thehydraulic cylinders each having outwardly extending lugs at top andbottom with the bottom lugs oriented in a different direction than thetop lugs, the platform comprising apertured projections for engagementby the lugs in a flrst orientation and for passing the cylinder and lugsin a second orientation, means for controlling the fluid pressure means,means on the supporting structure intermediate the pool top and floorfor arresting downward motion of the platform, in combination withindependent hoist means mounted above the storage pool for engaging andlifting the cask.

4. Apparatus for supporting a nuclear fuel shipping cask during loweringinto or raising from a storage pool, comprising a supporting structureat least partly immersed in and anchored to the pool, a cask supportplatform, fluid pressure responsive means supporting said platform andmounted on said supporting structure to provide vertical movement of theplatform from an upper position at the pool top to a lower position atthe pool floor, means for controlling the fluid pressure means, means onthe supporting structure intermediate the pool top and floor forarresting downward motion of the platform, in combination withindependent hoist means mounted above the storage pool for engaging andlifting the cask, a flanged base member having means for securing sameto the cask bottom, and a flexible substantially water-tight shroudsecured to the flanged base member and adapted to envelope the caskexterior.

5. Apparatus as set forth in claim 4 in combination with channel membersmounted at the pool top for guiding the flanged base member secured tothe cask onto the platform.

6. Apparatus for supporting a nuclear fuel shipping cask during loweringinto or raising from a storage pool, comprising a supporting structureat least partly immersed in and anchored to the pool, a cask supportplatform, fluid pressure responsive means supporting said platform andmounted on said supporting structure to provide vertical movement of theplatform along a vertical path from an upper position at the pool top toa lower position at the pool floor, said fluid pressure responsive meanscomprising hydraulic cylinders supporting the platform with saidhydraulic cylinders each containing a piston connected to and supportedby the supporting structure, means for causing said hydraulic cylindersto be selectively movable with and without said platform along saidvertical path, means for controlling the fluid pressure means, means onthe supporting structure intermediate the pool top and floor forarresting downward motion of the platform, in combination withindependent hoist means mounted above the storage pool for engaging andlifting the cask.

7. Apparatus as set forth in claim 6 wherein the selectively movablemeans comprises means for selectively supporting said platform at atleast two different locations along the length of the hydrauliccylinders.

8. Apparatus as set forth in claim 7 wherein the cylinders have a lengthabout one-half the pool depth.

9. Apparatus for supporting a nuclear fuel shipping cask as claimed inclaim 1 comprising:

a. a plurality of upright hollow posts;

b. a cable with a run disposed in each of said posts and having a runextending out of its associated post;

c. means for each of said posts around which is trained the associatedcable;

weight means disposed in each of said posts for up and down movement,each of said weight means being attached to the run of the cabledisposed in its associated post, each of said weight means forming afluid seal with its associated post;

each of said posts isfluid sealed around its associated cable above itsassociated weight means, each of said posts having a supply of fluidtherein between its fluid seal and its associated weight means; valvemeans on said posts disposed between the fluid seal of the associatedpost and its associated weight means for controlling the flow of fluidtrapped between the fluid seal of the associated post and the associatedweight means and escaping from its associated post; and

g. a shipping cask support attached to the runs of said cables extendingout of said posts to be supported thereby.

10. Apparatus as claimed in claim 9 wherein said shipping cask supportis disposed between said posts for up and down movement, and furthercomprising a fuel shipping cask seated on said shipping cask support.

11. Apparatus as claimed in claim 10 and including means with a plungeron each of said posts disposed a predetermined distance from the top ofits associated post, said plunger means being activated to move in thedownward path of travel of said cask support holding the same againstfurther downward movement within its associated post.

12. The combination as claimed in claim 10 wherein said fuel shippingcask includes means on the upper portion thereof adapted for engagementby the cable of acrane.

1. Apparatus for supporting a nuclear fuel shipping cask during loweringinto or raising from a storage pool, comprising a mechanical supportingstructure at least partly immersed in and anchored to the pool, a casksupport platform, fluid pressure responsive means supporting saidplatform and mounted on said supporting structure to provide verticalmovement of the platform along a path from an upper position at the pooltop to a lower position at the pool floor, means for controlling thefluid pressure means, mechanical stop means mounted on the supportingstructure intermediate the pool top and floor and selectively movableinto the vertical path of the platform for arresting downward motion ofand supporting the arrested platform, in combination with independenthoist means mounted above the storage pool for engaging and lifting thecask, said mechanical stop being capable of fully supporting the loadedplatform enabling disengagement of the hoist from the cask or of thefluid support for said platform.
 2. Apparatus as set forth in claim 1wherein the fluid pressure responsive means comprises hydrauliccylinders supporting the platform, said hydraulic cylinders eachcontaining a piston supported by the supporting structure.
 3. Apparatusfor supporting a nuclear fuel shipping cask during lowering into orraising from a storage pool, comprising a supporting structure at leastpartly immersed in and anchored to the pool, a cask support platform,fluid pressure responsive means supporting said platform and mounted onsaid supporting structure to provide vertical movement of the platformfrom an upper position at the pool top to a lower position at the poolfloor, said fluid pressure responsive means comprising hydrauliccylinders supporting the platform, said hydraulic cylinders eachcontaining a piston supported by the supporting structure, the hydrauliccylinders each having outwardly extending lugs at top and bottom withthe bottom lugs oriented in a different direction than the top lugs, theplatform comprising apertured projections for engagement by the lugs ina first orientation and for passing the cylinder and lugs in a secondorientation, means for controlling the fluid pressure means, means onthe supporting structure intermediate the pool top and floor forarresting downward motion of the platform, in combination withindependent hoist means mounted above the storage pool for engaging andlifting the cask.
 4. Apparatus for supporting a nuclear fuel shippingcask during lowering into or raising from a storage pool, comprising asupporting structure at least partly immersed in and anchored to thepool, a cask support platform, fluid pressure responsive meanssupporting said platform and mounted on said supporting structure toprovide vertical movement of the platform from an upper position at thepool top to a lower position at the pool floor, means for controllingthe fluid pressure means, means on the supporting structure intermediatethe pool top and floor for arresting downward motion of the platform, incombination with independent hoist means mounted above the storage poolfor engaging and lifting the cask, a flanged base member having meansfor securing same to the cask bottom, and a flexiblE substantiallywater-tight shroud secured to the flanged base member and adapted toenvelope the cask exterior.
 5. Apparatus as set forth in claim 4 incombination with channel members mounted at the pool top for guiding theflanged base member secured to the cask onto the platform.
 6. Apparatusfor supporting a nuclear fuel shipping cask during lowering into orraising from a storage pool, comprising a supporting structure at leastpartly immersed in and anchored to the pool, a cask support platform,fluid pressure responsive means supporting said platform and mounted onsaid supporting structure to provide vertical movement of the platformalong a vertical path from an upper position at the pool top to a lowerposition at the pool floor, said fluid pressure responsive meanscomprising hydraulic cylinders supporting the platform with saidhydraulic cylinders each containing a piston connected to and supportedby the supporting structure, means for causing said hydraulic cylindersto be selectively movable with and without said platform along saidvertical path, means for controlling the fluid pressure means, means onthe supporting structure intermediate the pool top and floor forarresting downward motion of the platform, in combination withindependent hoist means mounted above the storage pool for engaging andlifting the cask.
 7. Apparatus as set forth in claim 6 wherein theselectively movable means comprises means for selectively supportingsaid platform at at least two different locations along the length ofthe hydraulic cylinders.
 8. Apparatus as set forth in claim 7 whereinthe cylinders have a length about one-half the pool depth.
 9. Apparatusfor supporting a nuclear fuel shipping cask as claimed in claim 1comprising: a. a plurality of upright hollow posts; b. a cable with arun disposed in each of said posts and having a run extending out of itsassociated post; c. means for each of said posts around which is trainedthe associated cable; d. weight means disposed in each of said posts forup and down movement, each of said weight means being attached to therun of the cable disposed in its associated post, each of said weightmeans forming a fluid seal with its associated post; e. each of saidposts is fluid sealed around its associated cable above its associatedweight means, each of said posts having a supply of fluid thereinbetween its fluid seal and its associated weight means; f. valve meanson said posts disposed between the fluid seal of the associated post andits associated weight means for controlling the flow of fluid trappedbetween the fluid seal of the associated post and the associated weightmeans and escaping from its associated post; and g. a shipping casksupport attached to the runs of said cables extending out of said poststo be supported thereby.
 10. Apparatus as claimed in claim 9 whereinsaid shipping cask support is disposed between said posts for up anddown movement, and further comprising a fuel shipping cask seated onsaid shipping cask support.
 11. Apparatus as claimed in claim 10 andincluding means with a plunger on each of said posts disposed apredetermined distance from the top of its associated post, said plungermeans being activated to move in the downward path of travel of saidcask support holding the same against further downward movement withinits associated post.
 12. The combination as claimed in claim 10 whereinsaid fuel shipping cask includes means on the upper portion thereofadapted for engagement by the cable of a crane.